1. Field of the Invention
Embodiments of the invention generally relate to an apparatus for the distribution of gases within a process chamber.
2. Background of the Related Art
Integrated circuits have evolved into complex devices that can include millions of transistors, resistors and capacitors on a single chip. The evolution of chip design continually requires faster circuitry and greater circuit density that demand increasingly precise fabrication processes. One fabrication process frequently used is chemical vapor deposition (CVD). Chemical vapor deposition is generally employed to deposit a thin film on a substrate such as a semiconductor wafer. Chemical vapor deposition is generally accomplished by introducing a precursor gas into a vacuum chamber. The precursor gas is typically directed through a showerhead assembly situated near the top of the chamber. The precursor gas reacts to form a layer of material on the surface of the substrate as positioned on a heated support below the showerhead assembly. Volatile by-products produced during the reaction are pumped from the chamber through an exhaust system. One material frequently deposited on a substrate using chemical vapor deposition techniques is titanium.
One example of a titanium deposition is a chemical vapor deposition process that includes thermally decomposing titanium tetrachloride and hydrogen to deposit titanium on the substrate. The precursor gases generally flow through a showerhead to enhance deposition uniformity across the substrate. As this titanium deposition process is thermally driven, maintaining the showerhead at an elevated temperature enhances the titanium deposition rate. However, the elevated temperatures along with the chlorine rich environment of the reaction process and gases used to clean the showerhead often corrode the showerhead that is typically fabricated from aluminum. Coatings, such as nickel plating, are typically used to protect aluminum showerheads but often flake off, particularly near threaded holes where the plating may be damaged by fasteners allowing the underlying aluminum to be attacked. Particulates from the corroded showerhead assembly and flakes from the protective coatings may contaminate substrates during processing, resulting in costly chamber downtime and substrate defects.
State of the art showerheads are generally fabricated from a single element or mass of material. These showerheads include a mounting portion circumscribing a perforated faceplate. Since the faceplate portion of the showerhead is subjected to greater heat than the mounting portion during processing, thermal gradients exist in the showerhead that highly stress the faceplate and often result in cracking or warping of the faceplate.
Moreover, the lid that supports the showerhead is typically cooled to prevent premature reaction and deposition of titanium within the lid. The cooled lid further accentuates the temperature difference/gradient between the mounting portion and the faceplate of the showerhead, and heightens the probability of the faceplate of the showerhead to crack or warp as it is thermally cycled over its life, particularly when used at process temperatures in excess of 350 degrees Celsius. A cracked or warped showerhead disrupts the flow uniformity of gases passing through the showerhead, resulting in poor deposition uniformity thereby necessitating replacement of the showerhead.
Therefore, there is a need for an apparatus for the distribution of gas in the chemical vapor deposition chamber.
In one aspect of the invention, a showerhead assembly for distributing gases within a processing chamber is provided. In one embodiment, a showerhead assembly for distributing gases within a processing chamber includes a cylindrical member having a faceplate coupled thereto. The cylindrical member has an outwardly extending first flange at a first end. The faceplate is coupled to a second end of the cylindrical member and has a plurality of holes formed though a center region of the faceplate.
In another embodiment, a showerhead assembly for distributing gases within a processing chamber includes a faceplate disposed between a cylindrical member and at least one clamp member. The clamp member is urged against the cylindrical member, thereby clamping the faceplate therebetween.
In another embodiment, a showerhead assembly for distributing gases within a processing chamber includes a cylindrical member, a disk and a means for clamping the disk to the cylindrical member that allows movement of the disk relative to the cylindrical member.
In another aspect of the invention, a processing chamber is provided. In one embodiment, a processing chamber includes a chamber body having walls and a bottom defining a processing region, a substrate support disposed in the processing region and a gas box supported by the walls and having a fluid channel disposed therethrough, a cylindrical member supported by the walls and a faceplate coupled to the cylindrical member. The cylindrical member is comprised of nickel and has an outwardly extending first flange at a first end that is disposed between the gas box and the walls of the chamber body. A second end of the cylindrical member extends into the processing region. The faceplate is comprised of nickel or graphite and is coupled to the cylindrical member at the second end. The faceplate has a plurality of holes formed though a center region of the faceplate.